Paramagnetic fluid analyzer utilizing toroidal fluid containers and an inductance bridge



r 3,447,073 OIDAL FLUID DGE May 27, 1969 5. w. GAMBLE PARAMAGNETIC FLUID ANALYZER UTILIZING TOR CONTAINERS AND AN INDUCTANCE BRI Flled Oct 26 1966 Sheet Tllc i RNEYS May 27, 1969 w, GAMBLE Y 3,447,073

' PARAMAGNETIC FLUID ANALYZER UTILIZING TOROIDAL FLUID CONTAINERS AND AN INDUCTANCE BRIDGE Filed Oct. 26. 1966 Sheet 3 of 2 comp/1 RE INV TOR 750295 74 M846 ATTO NEYS United States Patent US. Cl. 32436 2 Claims ABSTRACT OF THE DISCLOSURE Paramagnetic fluid is supplied to a hollow toroid container and magnetized together with a separate non-magnetizable reference toroid; The difference of magnetic fluxes in the two toroids is detected by an inductance bridge circuit.

The present invention relates to a paramagnetic fluid analyzer such as for example an oxygen analyzer. The oxygen analyzer of the present invention provides a method for analyzing the oxygen content of a process gas. Results of this analysis can be used in combustion or process control, product control, safety (0 in inert or explosive gases), or other applications.

In order that the present invention may be readily carried into effect, it will now be described with reference to the accompanying drawing, wherein:

FIG. 1 is a circuit diagram of an embodiment of the oxygen analyzer of the present invention;

FIG. 2 is a view of a toroid and winding of the embodiment of FIG. 1;

FIG. 3 is a winding diagram of the embodiment of FIG. 1;

FIG. 4 is a circuit diagram ofa modification of the embodiment of FIG. 1; and

FIG. 5 is a circuit diagram of another embodiment of the oxygen analyzer of the present invention.

Among the more common process gases, oxygen and two oxides of nitrogen, NO and N0 are unique in that they are paramagnetic (attracted by a magnetic field); other gases are slightly diamagnetic (repelled by a magnetic field). However, NO and N0 seldom occur as constituents of industrial gases and the magnetic property of diamagnetic gases is so small as to be insignificant.

In FIG. 1, which is an embodiment of the magnetic oxygen analyzer of the present invention, T is a toroid container adapted for receiving through an inlet 5 the sample fluid to be analyzed. T is a reference toroid whose core is non-magnetic. They are not field coupled. Windings 1, 2, 3 and 4 form a bridge circuit such that opposite legs are associated with the same toroid. The bridge is balanced without sample.

Presence of oxygen in T will cause an increase in inductance and therefore its impedance to time varying currents. Windings are as shown in FIG. 2. The detector records the unbalance which is double that which would result from sample in only one leg. The cross coupling shown in the equivalent circuit represents the transformer action between windings on the same core. The remaining analysis follows conventional impedance bridge theory.

The configuration of FIG. 4 is a somewhat dilferent approach to the balance and compare idea and is an instrument which provides good stability and calibration.

In FIG. 4, T and T are again sample and reference toroids wound as in FIG. 2, but note the sense of the Windings. The primaries are in series so that the same current flows through them and the primary of the reference transformer T T and T cores are magnetized in the same direction by primary current. However, S and S are Wound or connected (it makes no dilference) so that their induced voltages tend to cancel each other in the external circuit.

The windings are adjusted for E E =0 without sample and a high primary current rate of change.

E is a measure of the primary current change. The ratio of inputs to the compare circuit is E volts peak then with pure oxygen as the sample:

E --E =0.00002 volts (approximately) =20 microvolts Measuring circuits to a few microvolts are available or it should be practical to produce higher secondary voltages to ease the detection problem.

The difference in toroid core flux density may be determined in a manner similar to the aforedescribed manner, but not utilizing a bridge technique, to determine the presence of oxygen in the sample fluid. In FIG. 4, the difference o-f'the outputs of the two toroids T and T is compared with a sample of the magnetizing force, provided by the reference transformer T to provide the relative difference of the permeability of the toroid cores. A single secondary winding enclosing both toroids T and T pro duces a voltage which varies in magnitude as the difference in the rate of change of magnetic flux in both said toroids. This is shown in FIG. 5.

What is claimed is:

1. A paramagnetic fluid analyzer, comprising a sample container having a toroid configuration, a sample winding wound around said sample container; a reference container having a toroidal configuration whose core is nonmagnetic; a reference winding wound around said reference container; a third and fourth winding wound respectively around said'sample container and said reference container; circuit means connecting said sample winding,

said reference Winding, and said third and fourth windings as legs of an inductance bridge, for supplying the same magnitude of electrical current through said windings, and for indicating any unbalance of said bridge; and fluid supply means for supplying a sample fluid to said sample container; so that When said windings are energized by said current therethrough and said sample fluid contains a paramagnetic fluid the electrical impedance of said sample winding and said third winding increases thereby unbalancing said bridge to an extent corresponding to the amount of paramagnetic fluid in said sample fluid.

2. An analyzer according to claim 1 wherein said paramagnetic fluid is oxygen.

References Cited UNITED STATES PATENTS 2,608,621 8/1952 Peterson 324-34 2,867,118 1/1959 Cavanagh 324-34 3,076,929 2/ 1963 Gillerman 32436 3,271,664 9/1966 Mountz et a1 324-37 RUDOLPH V. ROLINEC, Primary Examiner.

10 R. J. CORCORAN, Assistant Examiner.

U.S. Cl. X.R. 73-23 

